© 2017, Saudi Arabian Armed Forces Hospital. All rights reserved.Objectives: To determine the associations between serum cancer antigen 15-3 levels and prognostic factors in patients with endometrial carcinomas. Additionally, we investigated the clinical utility of serum cancer antigen 15-3 levels in the selection of low-risk patients with endometrioid type, tumor size <2 cm, myometrial invasion ≤50%, and histological grade 1-2. Methods: Ninety-six patients, who were surgically staged at Ankara Yildirim Beyazit University, Ankara, Turkey, between 2007 and 2016, were retrospectively analyzed. Demographic, clinical, and surgical characteristics were retrieved from the patients’ hospital records. A p<0.05 was considered significant. Results: Fifteen patients had advanced (≥Stage II) disease, 14 patients had Type 2 histology, 20 patients had Grade 3 tumors, 23 patients had lymphovascular space invasion, and 10 patients had positive lymph node involvement. Serum cancer antigen 15-3 levels were significantly higher in patients with advanced (≥Stage II) disease, Type 2 histology, Grade 3 tumors, lymphovascular space invasion, and positive lymph node involvement (p<0.05). Serum cancer antigen 15-3 levels were also significantly correlated with tumor size (p=0.006). Serum cancer antigen 15-3 levels were significantly lower (95% confidence interval: 0.57−0.79; p=0.03) in low-risk patients compared to other endometrial carcinoma patients. A cutoff of 25.0 IU/mL was used to identify high-risk patients with a specificity of 100%. Conclusion: Serum cancer antigen 15-3 levels significantly correlated with prognostic factors and were a useful diagnostic tool for endometrial carcinomas.